Flight log analysis after crash (motor obstructed)

[Mosherf]

Had a crash 2 days ago just after take off.
flight log here: DJIFlightRecord_2021-09-28_[06-38-31].txt
screenshots attached
seems like a failure in one of the motors.
testing the drone without props - goes to 980 RPM with no warning message on DJI GO 4.
Want to repair the drone but - How can I tell which motor failed out of the 4? Is it possible using DatCon or Airdata?
DJI offers analysis service for 35 USD.

Thanks.

https://imgur.com/Cnb6p0d

https://imgur.com/jr1DCW4

 

[Mosherf]

Also attached another type of flight log extracted with Datcon: 21-09-28-06-37-24_FLY024.log.txt

 

[Deleted member 103366]

Can you post the logs directly to the forum as attachments to a post?
You might also want to look for the DAT file, if you are using an RC1B contoller you I doubt you will have one. It will have a similar time stamp but maybe an hour out (some of my DATs have this difference others do not) but in general the DAT's minute and or second stamps are slightly before the time stamp of the txt. Also some of the DAT time stamps are in the 24hr clock and others in a 12hr clock .

 

[Mosherf]

Yes, this is the flight log from the DJI GO4 app folder

 

[Mosherf]

This is the flight log generated from the DAT file, using DatCon

 

[Mosherf]

screenshots

 

[Deleted member 103366]

Can you post the unprocessed DAT?

 

[Mosherf]

Yes, These are from the app folder (not from the drone)

 

[Deleted member 103366]

Ooooo your going to want some of the gurus to look at this, the attached is what CsvView (working on the DAT) shows as the motor speeds

If the other logs are from the drone how are you getting them? Are you using extractdji or something?

 

[Mosherf]

Ooooo your going to want some of the gurus to look at this, the attached is what CsvView (working on the DAT) shows as the motor speeds

If the other logs are from the drone how are you getting them? Are you using extractdji or something?

They are not from the drone, but from the dji go go4 app folder on my phone.

Looks like the green - left front motor in the one that failed - doesn't it?

 

[Deleted member 103366]

I don't know enough to say, but the last few seconds of the flight are odd. That said would a failed motor increase and decrease its speed like that? I'd think it was more likely to slow. Was the prop intact and properly attached when you recovered the drone?

Did the drone fly over an object at around 17.3 seconds?
Though the drone was, for no reason that I can see, descending 'gradually' the, what I understand to be the VPS height ("waveheight"), plummets from 2.1m to 0m in under 0.1seconds

 

[Meta4]

Had a crash 2 days ago just after take off.
flight log here: DJIFlightRecord_2021-09-28_[06-38-31].txt

Your flight data shows a problem starting at around 16.1 seconds into the flight when you briefly pulled the left stick down fully.
The drone pitched forward, well past the normal level and rolled to the right past 90° and it spun clockwise and rapidly lost height.

This indicates loss of thrust from the front right, caused by failure of either the motor or prop.

Collision with the ground occurred at 17.2 seconds and all data and warnings after that are a result of the crash, not things that might have caused it.

 

[Meta4]

They are not from the drone, but from the dji go go4 app folder on my phone.

Looks like the green - left front motor in the one that failed - doesn't it?

The green indicates one motor trying to compensate for the problem in the red motor.

 

[Meta4]

Did the drone fly over an object at around 17.3 seconds?
Though the drone was, for no reason that I can see, descending 'gradually' the, what I understand to be the VPS height ("waveheight"), plummets from 2.1m to 0m in under 0.1seconds

VPS gives erratic (and useless) data when the drone is rolling and tumbling.

 

[Mosherf]

I don't know enough to say, but the last few seconds of the flight are odd. That said would a failed motor increase and decrease its speed like that? I'd think it was more likely to slow. Was the prop intact and properly attached when you recovered the drone?

Did the drone fly over an object at around 17.3 seconds?
Though the drone was, for no reason that I can see, descending 'gradually' the, what I understand to be the VPS height ("waveheight"), plummets from 2.1m to 0m in under 0.1seconds

Yes the props were intact on the ground and well attached. The motors continued to spin after the crash, until I shut them down with the RC sticks.
There were no objects around the drone as far as I remember. I saw the drone lining towards one corner (I'm almost sure it was front-right), and so I tried to bring it back manually and land it. It was very unstable and one I tried to lower it, it lost balance and crashed.

 

[Mosherf]

Your flight data shows a problem starting at around 16.1 seconds into the flight when you briefly pulled the left stick down fully.
The drone pitched forward, well past the normal level and rolled to the right past 90° and it spun clockwise and rapidly lost height.

This indicates loss of thrust from the front right, caused by failure of either the motor or prop.

Collision with the ground occurred at 17.2 seconds and all data and warnings after that are a result of the crash, not things that might have caused it.

Thank you for your reply.
I believe pulling the left stick down fully was me trying to land the drone once I saw it wasn't stable (lining towards one of the corners).
Can you please indicate to me where does it show crashing at 17.2?

Your flight data shows a problem starting at around 16.1 seconds into the flight when you briefly pulled the left stick down fully.
The drone pitched forward, well past the normal level and rolled to the right past 90° and it spun clockwise and rapidly lost height.

This indicates loss of thrust from the front right, caused by failure of either the motor or prop.

Collision with the ground occurred at 17.2 seconds and all data and warnings after that are a result of the crash, not things that might have caused it.

Is it definitely the front right motor?
thanks.

 

[Meta4]

Can you please indicate to me where does it show crashing at 17.2?

That's when the altitude reached zero after a very short flight.

Is it definitely the front right motor?
thanks.

Yes

 

[Mosherf]

Hi guys, another question please.
Could the motor failure be caused by small gravel that entered *the body part of the drone*? Or the motor is only located underneath the props?

I'm not sure, but after the crash when I cleaned the drone at home and shaked it, I could here small particles moving and that was gravel. All of if went out and now there's no sound of moving parts.
I'm not sure if they gravel caused the motor problem or that it found its way in when the drone rolled on the ground.

Thanks!

 

[Deleted member 103366]

Gravel and or sand can stop a motor.
With the props removed I'd turn the drone upside down and put the suspect motor to the nozzle of a vacuum cleaner then slowly turn the motor by hand. Do not force anything and if it jams turn the motor to and fro.
Pay attention to how the motor feels and compare it to the other motors.


The drone of the attached photos was in the sea for several days and all the motors are jammed SOLID, either through sand or corrosion or both.
To expose the screws holding the front motor you have to remove the landing leg and it is held by 3 visible screws and a 4th hidden screw which is under the LED cover/lens
Prise the LED cover out from the top and DO NOT let the tool go too far under the cover, from memory there is a risk of hitting the actual LEDs.

 

[Mosherf]

Partial Update: The technician at the lab says its more likely that one of the 3 pins of the propeller broke (picture attached) and jammed the motor, rather than a spontaneous motor failure.

Today I flew the drone with new props, just a few centimeters above ground and it seemed fine.